1. Field of the Invention
The present invention relates to a multichannel magnetic head using magnetoresistive effect, mounted on a drive apparatus for driving a magnetic recording medium such as a magnetic disk or a magnetic tape, in order to read out recorded information from a plurality of tracks on these magnetic recording media.
2. Description of Related Art
As a reproducing magnetic head for reading out recorded information from a magnetic recording medium such as a magnetic tape or a magnetic disk, for example, a magnetic head using magnetoresistive effect has widely been used as a high recording density reproducing head, in particular, because the magnetic head using magnetoresistive effect can obtain high sensitivity.
When the magnetic head using magnetoresistive effect is employed as the reproducing head as described above, a recording and reproducing head is comprised of a combination of a magnetic head using magnetoresistive effect and an electromagnetic induction type magnetic head, for example.
When a multichannel magnetic head is comprised of this recording and reproducing magnetic head, it is unavoidable that the number of terminals led out from the multichannel magnetic head increases enormously.
FIG. 1 of the accompanying drawings is a schematic diagram showing a magnetic tape drive apparatus to which a multichannel magnetic head using magnetoresistive effect according to the present invention can be applied.
As shown in FIG. 1, in a magnetic tape drive apparatus for driving a magnetic tape 101, the magnetic tape 101 is supplied from a magnetic tape supply reel 103 within a tape cassette 102, guided by a plurality of guide rollers 104 and wound around a magnetic tape take-up reel 105.
Then, during the magnetic tape 101 is being transported, a multichannel magnetic head 100 comes in slidable contact with the magnetic tape 101 to record and reproduce information on and from the magnetic tape 101 in a multichannel fashion.
FIG. 2 is a schematic plan view showing a main portion of this multichannel magnetic head 100, and FIG. 3 is a schematic cross-sectional view taken along the line IIIxe2x80x94III in FIG. 2, for example. As illustrated, in the multichannel magnetic head 100, a first magnetic shield 131 and a first magnetic gap layer 141 are formed on a first guard substrate 121, for example, and thereupon are parallelly disposed a plurality of magnetoresistive effect type reproducing magnetic head elements 106 facing the front end at which this magnetic head 100, for example, comes in slidable contact with a magnetic recording medium (not shown), i.e., a sliding surface S. Leads 106L made up of conductive layers respectively formed into required patterns are extended from sense current feeding electrodes toward the rear end edge on the opposite side of the sliding surface S.
On these reproducing magnetic head elements 106, there is formed an insulating layer 107, on which a second magnetic gap layer 142 having a predetermined thickness is formed. A second magnetic shield 132 is formed on the second magnetic gap layer 142.
Then, on the second magnetic shield 132, there are parallelly disposed electromagnetic induction type recording magnetic head elements 108 facing the sliding surface S corresponding to the respective reproducing magnetic head elements 106.
As shown in FIG. 3, each of the recording magnetic head elements 108 comprises an insulating non-magnetic layer 109 formed on the second magnetic shield 132, for example, a thin-film coil 110 formed on the insulating non-magnetic layer 109 and a belt-like magnetic core 111 formed on this thin-film coil 110 through an insulating e layer in such a manner that its front end faces the sliding surface S.
The magnetic core 111 has at the central portion of the thin-film coil 110 through-holes penetrating the non-magnetic layer 109 formed on the second magnetic shield 132 and an insulating layer formed on the non-magnetic layer 109. The respective magnetic cores 111 are magnetically coupled to the magnetic layers made up of the second magnetic shields 132 through these through-holes, and a closed magnetic circuit is formed of the magnetic core 111 and this magnetic layer. In this manner, there is constructed the electromagnetic induction type recording magnetic head element 108 around which the thin-film coil 110 is wound and in which a magnetic gap g is formed at the front end of this closed magnetic circuit by the non-magnetic layer 109 having a required thickness.
On these recording magnetic head elements 108, there is formed a non-magnetic insulating layer 112 on which a third magnetic shield 133 and a second guard substrate 122 are formed.
At that very time, the rear end edge of the insulating non-magnetic layer 109, for example, is exposed to the outside.
At the rear end edge of this non-magnetic layer 109, there are parallelly disposed sense current feeding terminals 151 and 152 for the respective reproducing magnetic head elements 106, and terminals 161 and 162 for the thin-film coils 110 of the respective recording head elements 108.
The terminals 161 and 162 have connected thereto end portions of leads 108L made up of conductive layers led out from both terminals of the respective thin-film coils 110 of the respective recording head elements 108.
On the end portions of the sense current feeding leads 106L of the respective reproducing magnetic head elements 106 as are extended below the rear end edge of the insulating layer 112, there are bored through-holes 150 which are communicated with these leads 106L. Leads 106L are each connected to the respective terminals 151 and 152 by a conductive layer formed within this through-hole 150.
As described above, in the ordinary multichannel magnetic head, since two terminals are respectively led out from the respective magnetoresistive effect type reproducing magnetic head elements 106 and recording magnetic head elements 108, there are led out at least four terminals 151, 152 and 161, 162 with respect to each channel.
As a result, it is unavoidable that the number of terminals increases enormously and that the portion in which the terminals are arrayed occupies a large area of the whole of the magnetic head. This hinders the multichannel magnetic head from being miniaturized.
Moreover, in order to miniaturize the whole of the multichannel magnetic head, the space between the terminals and the space between the leads should be decreased by decreasing the width of the terminals or by reducing the widths of the lead portions themselves from which the terminals are led out. In this case, however, a resistance at the portion from which the terminal is led out increases, poor insulation, short-circuit occur between the terminals or between the leads and so forth, which causes characteristics of the magnetic head element to be fluctuated. Moreover, it is unavoidable that reliability and a yield of the magnetic head element are lowered.
In view of the aforesaid aspect, it is an object of the present invention to provide a multichannel magnetic head using magnetoresistive effect in which the number of terminals can be decreased.
It is another object of the present invention to provide a multichannel magnetic head using magnetoresistive effect in which the whole of a multichannel magnetic head can be miniaturized.
It is still another object of the present invention to provide a multichannel magnetic head using magnetoresistive effect in which the occurrence of short-circuit and poor insulation between the terminals or between the leads can be removed.
It is a further object of the present invention to provide a multichannel magnetic head using magnetoresistive effect in which the occurrence of fluctuations of element characteristics can be removed.
It is yet a further object of the present invention to provide a multichannel magnetic head using magnetoresistive effect which can become highly reliable.
It is still a further object of the present invention to provide a multichannel magnetic head using magnetoresistive effect the yield of which can be improved.
According to an aspect of the present invention, there is provided a multichannel magnetic head using magnetoresistive effect which is comprised of a first magnetic shield, a second magnetic shield, the first and second magnetic shields being opposed to each other and a plurality of magnetoresistive effect type reproducing magnetic head elements parallelly arrayed between the opposing first and second magnetic shields, wherein at least the first magnetic shield is formed of a conductive soft magnetic material.
The reproducing magnetic head elements comprised of ferromagnetic tunnel type magnetoresistive effect elements are parallelly arrayed on the first magnetic shield.
Electrodes on one side for applying the sense current to these ferromagnetic tunnel type magnetoresistive effect elements in the direction crossing a tunnel barrier layer are commonly constructed by the first magnetic shield and led out as a common one terminal.
Further, the multichannel magnetic head using magnetoresistive effect according to the present invention can be modified as a contact type magnetic head which comes in contact with a magnetic recording medium.
As described above, the multichannel magnetic head using magnetoresistive effect according to the present invention is comprised of the reproducing magnetic head elements formed of the ferromagnetic tunnel type magnetoresistive effect elements (TMR elements). One magnetic shield disposed across these magnetic head elements serves as electrodes on one side for applying the sense current to these ferromagnetic tunnel type magnetoresistive effect elements, whereby electrodes on one side for a plurality of reproducing magnetic head elements can be made common.
As described above, with respect to the reproducing magnetic head elements formed of a plurality of TMR elements, since electrodes on one side can be led out as one terminal, the number of the terminals can be decreased considerably, whereby the area of the portion in which the terminals are arrayed can be reduced and the interval between the terminals and the interval between the leads can be increased.
Furthermore, since this TMR element is the element having a large resistance with respect to the direction in which the sense current is applied, when a contact type magnetic head which comes in contact with a magnetic recording medium is comprised of this TMR element, even though the area of the reproducing head element is increased, sufficiently large resistance can be maintained so that a high magnetoresistive effect ratio (MR ratio) can be obtained.